Time-limit relay.



J. R. CRAIGHEAD.

TIME LIMIT RELAY.

APPLICATION man SEPT. 2. 1914.

Patented Dec. 18, 1917.

Im ntor Jam 5 RCrajghead, QM M Witnesses H is Attorney.

25 verse time limit characteristic of any de- JAMES R. GRAIGI-IEALD,

or SCHENECTADY, NEW YORK, Assrenon r GENERAL Enrio'rnrc COMPANY, A CORPORATION OF NEW YORK.

TIME-LIMIT RELAY.

i To all ibhom it may concern:

'. larity in the appended claims.

Be it known that I, JAMEs' R. CRAIG-HEAD,

a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Time-Limit Relays, of which the following is a specification.

My present invention relates to relays and particularly to relays designed to protect electrical installations from the injurious effects of overloads and similar abnormal conditions. More specifically, my invention relates to relays used for controlling protective devices for electrical apparatus.

The object of my invention is to provide a novel and improved construction of relay and especially a relay construction having a time limit which will be variable for varying strength of current in the circuit to which it is connected. A further object of my invention is to provide a relay construction in which the various elements may be so proportioned that the device has an ingree desired.

, In carrying my invention intoefi'ect, I employ twocotiperatin movable contacts connected to two mova ble elements which which the relay is connected. The two contacts are arranged to travel in'the same path in the same direction and are normally separated from each other. The movable elements are so constructed, however, that when the current in predetermined amount, one contact will quickly assume a position which is a measure of the load and the other contact will follow over the same path toward the first contact at a rate which is a measure of the load and will overtake the first contact, and thus, close I a circuit and operate the protective apparatus controlled by the relay. By varying the characteristics of the movable elements, the time characteristic of the relay may be varied as desired.

The features of my invention which I consider novel arepointed out with particu- The construction and mode of operation ofa relay embodying the features of my invention will.

best be understood, however, from the following description taken in connection with Specification of Letters Patent.

vure 1 is a diagrammatic view of the time limit type to be the circuit exceeds a Patented. Dec. 18, 1917.

Application filed September 2, 1914. Serial No. 859,849.

in which Figin perspective of a relay embodying my invention and connected to a circuit breaker in an electric installation, and Fig. 2 illustrates one relation which may be given to the scale characteristics of the two movable elements of the relay.

As indicated in the drawing, the relay comprises two indicating meter elements or ammeter elements having two movable disk armatures 1 and 2, which are rotated in the direction of the arrows by motive elements having current coils 3 and 4 respectively connected to the circuit 5 supplying apparatus 6 which is to be protected. It is understood that the magnetic circuits of the coils 3 and 4; are provided with the usual shading coils to enable them to exert a torque on their respective disk armatures. The movement of the armatures 1 and 2 is resisted by springs 7 and 8. Contacts 9 and 10 are connected to the armaturcs and so mounted that when the armatures revolve, they will travel over the same path. As long as the current in the circuit does not exceed a predetermined the accompanying drawings,

amount, the two contacts will not touch each other. The movable elements are so de signed, however, that when the current does exceed the desired amount, contact 9, called the leading contact will travel quickly and take up a certain position and contact 10 called the following contact. and which is simultaneously operated, will follow in the path of contact 9 and will travel far enough to overtake contact 9 and thus close circuit 11 and energize the trip coil 12 of the circuit breaker 13. Electrical connection may c'onveniently he made between the circuit 11 and the contacts 9 and 10 through the springs 7 and 8 and the armature shafts 14 and 15, as indicated. j I

Armature 1 is lightly dumped by the usual damping magnet 16, while armature 2 is more strongly damped by another stronger magnet 17. \Vith this arrangement, the speed of movement of the armature l'is rendered greater than that of armature 2 and hencecontact 9 is moved more quickly than contact 10 and it will be seen that upon the occurrence of an overload sufficient to actuate the relay, that contact 9 quickly to a certain position, while armature 2 will cause contact 10 to follow contact 9 more slowly until it engages contact 9 and closes theitrippingcircuit, the

k armature 1 Wlll carry" reached the end of its travel.

two contacts not being able to come together until after the lightly damped armature has If the springs 7 and 8 on the two ammeter elements exert equal torques, the path of movement of each of the disk armatures 1 and 2 would be equal and the contacts 9 and 10 would not come into engagement until the heavily damped element 2 reaches the end of its natural travel, that is, where the torque exerted on the disk is balanced by the countertorque exerted by its spring, the distance traveled being the measure of the load on the circuit. With this arrangement the two movable contact elements 1 and 2 would have the same scale characteristics, the distance traveled varying as a function of the current in the circuit. As the torque varies with the square of the. current, however, the velocity may be made to increase in substantially the same proportion as the distance traveled so that the relay will have a practically definite time element, that is the leading contact 9 always determines the limit of travel of the following contact 10 and if the two contacts have the same limit of travel, the leading contact 9 is always positioned 'at the limit of travel or" contact 10 where engagement of the contacts takes place, thus although the leading contact is positioned at a greater distance, the greater the overload and the following contact 10 has to cover this greater distance to engage contact 9, still the following contact moves this greater distance in the same time, as the speed of movement of the disk increases at the same rate as the distance over which it has to move increases. If, however, the leading element were stationary, the time required to closethe contacts would vary inversely nearly as the square of the current. Hence by varying the relation between the scale characteristics of the two elements, the relation between time and applied current may be adjusted so as to give a time limit characteristic which is any inverse function desired -of the applied current.

In Fig. 2 I have indicated a relation which may be given to the scale characteristics of the two elements. The upper scale is that of the lightly damped element which is designed to have a shorter natural travel for the same current value than the more heavily damped element. This may easily be'accomplished in several ways such as varying the shape of the disk by making the spring 7 stronger than the spring 8 or by making'the coil 4 stronger than the coil 3.

In the construction shown, I have made the spring 7 stronger than the spring 8. Upon the tWo scales shown in Fig. '2 the numbers denote the current values which cause an angular deflection of the amount shown by the corresponding divisions, that the lower scale.

is, a current of 7 amperes through the current coils 3 and 4 will cause an angular deflection of the armature 1 such that contact 9 takes up a position corresponding to the division 7 on the upper scale, While the angular deflection of the armature 2 would be such that contact 10 would be moved to a position corresponding to the division 7 on Due to the countertorque exerted by the spring 7 being greater than that exerted by spring 8, contact 9 will move over a shorter path than the contact 10 and due to the fact that armature 1 is more lightly damped than armature 2, the leading contact 9 will move over its shorter path and reach its position corresponding to 7 amperes before the following contact 10. The position assumed by the leading contact 9, therefore, always limits the path of the movement of following contact 10 so that when contact 10 reaches the contact 9 it comes into firm and positive engagement with contact 9 because the armature 2 still has sufficient torque to carry it to the full extent of its travel.

It will be understood that contact 10 moves -from initial position to its position corresponding to any current value, that is, completes its natural path of movement for every current value in approximately the same time. For (3 amperes. for instance, the contact 10 moves to the position marked 6 on its scale in the same time that 19 amperes will cause the contact 10 to move to the position marked 10. In order to obtain inverse time characteristics, I so proportion the path of movement of the leading contact to the path of movement of the following contact that the difference between the paths of movement increases as the load or current on the circuit increases. It takes, for ex ample, 5 seconds for the following contact to move under 6 amperes up to the, point 6 on the lower scale but the contact 10 only moves to the first 6 on the upper scale which is the point where it engages-the leading contact. The time that it takescomact 10 to overtake contact 9 is therefore that part of 5 seconds which the path of movement of the contact 9 is to the natural path of movement of contact 10. If 10 amperes exist the contact 10 would move from its initial position to the point 10 on the lower scale in the same time, namely 5 seconds, but its path of movement is limited to the position marked 10 on the upper scale which means that contact 10 overtakes contact 9 in that part of 5 seconds which the path of movement of contact 9 is to the natural path of movement of contact 10. Hence by varying the torque of the spring 7 the path ,of movement of contact 10 is varied so that the time characteristics of the relay can be made anything desired.

It is understood that contacts 9 and 10 may be connected directly to the circuit 5 to menace load, in this case 5 amperes, to close its contacts 19 and connect the current coils 3 and 4 in circuit. In such a case the scale shown in Fig. 2 below the 5 amperes indication is not used as the movement of the armature elements over this portion of the scale is breaker by reason of 7 cording to my prevented by the relay 18 holding'their circuit open. I prefer, however, to use the overload relay 18, as the connection of the elements directly in circuit is liable to cause floating of the contacts under certain conditions of load which if followed by an overload will cause an operation of the relay in a shorter time than is intended.

Thisv willcause the coils 3 and 4 to be en- -ergized by a. current which is proportional to the current in circuit 5, but they will be energized only so long as the current equals or exceeds the predetermined value, as the relay 18 will allow contact 19 to be broken as soon as the current falls below The tripping circuit 11 may also be closed and opened as indicated by contact 19 in order to avoid the operation of the circuit the lightly damped Contact overtaking the more heavily damped contact 10 in returning to the zero position when the energizing current is thus cut oif from the magnetizing coils. Consequently 3 the relay will not open the circuit upon the occurrence of a transitory excess current of shorter duration than the'time limit of the relay for that particular value of current.

I For the purpose of illustration I have explained the principle-of my invention in connection with the actuating means of the indicating meter type. It will, of course, be understood, however, that my invention is not limited to actuating means of this particular type but that many variations in the means employed for-moving the contacts may be made without departing from the scope of the appended claims. he understood that a relay constructed acinvention is not limited in its usefulness to the particular application which'Ihav'e shown and described.

' What I claim as new'and desire to secure by Letters Patent of the United States, is:

1. A relay comprising in' combination two meter elements having magnetizing coilsand rotatable armaturcs mounted in the magnetic fields of said 00118 and contact that value.

It will also 2 members attached to each of said armatures 1 1n such a Way as to travel in the same direction over the same path when the armaturesrotate, sa1d contact members being normally separated from each other and the meter elements being so proportioned that the contact members will touch each other when the magnetizing current exceeds a predetermined amount.

2. The combination in .a relay of a meter elementv having a magnetizing coil arid a. lightly magnetic field of said coil, a second meter element having a magnetizing coil and a more heavily dam ed armature than the first, a contact mem er attached to the armature of the first element so as to rotate therewith and a second contact member attached to the armature of the second meter element so as to rotate therewith and follow the same path as the first contact member, said contact members being normally separated from each other and the meter elements damped armature mounted in the being so proportioned and so related to each 7 other that the second contact will overtake the first when the magnetizing current exceeds a predetermined amount.

3. The combination in a relay of a meter element having a magnetizing coil and a lightly damped armature mounted in the magnetic field of sa1d coil, 'a second .meter element having a magnetizing c011 and a more heavily damped armature than the first,

a contact member attached to the armature of,

the first element so as to rotate therewith and a second contact member attached to the armature of the second meter element so as to rotate therewith and follow the same path as the first contact member, said contact members being normally separated from each other and the scale characteristics of the two elements being such that the second contact will overtake the first when the magnetizing current exceeds a predetermined amount.

4. The combination in a relay of a meter element having a magnetizing coil and a lightly damped armature mounted in the magnetic field of said coil, 2. second meter element having a magnetizing coil and a more heavlly damped armature than the first, a contact-member attached to the armature of the first element so as to rotate therewith and a second contact member attached to the armature of the second meter element so as to rotate therewith and follow the same path as the first contact member, said contact members being normally separated from each other and the meter elements being so proportioned and so related to each other that the second contact will overtake the first when the magnetizin'gcurrent exceeds a predetermined amount and that thetime required for second contactnto overtake the first after the excess current has been 1 ing each'of said contacts 1n the samed-irection,

applied will vary as an inverse-function of the amount of the applied current.

5. The combination in a relay of a meter element having a magnetizing coil and a lightly damped armature mounted in the magnetic field of said coil, a second meter element having a magnetizing coil and a more heavily damped armature than the first, a contact member attached to the armature of the first element so as to rotate therewith and a second contact member attached to the armature of the second meter element so as to rotate therewith and follow the same path as the first contact member, said contact members being normally separated from,

each other and the scale characteristics of the two elements being such that the second contact will overtake the first when the magnetizing current exceeds a predetermined amount and. that the time required for second contact to overtake the first after the excess current has-been applied will vary as an inverse function of the amount of the applied current.

6. The combination in a relay of two normally separated contacts, and actuating means for each of said contacts for causing said contacts to travel over the same path in the same direction, the actuating, means for said contacts being so proportioned that one of the contacts will touch the other when the actuating current exceeds a predetermined amount.

7 The combination in a relay of two normally separated contacts, and actuating means for each of said contacts for causing said contacts to travel over the same path in the same direction, the actuating means for said contacts'being so proportioned that the leading contact will reach the end of its travel sooner than the following contact and that the following contact will overtake the leading contact when the actuating current exceeds a predetermined amount.

4, 8. The combination in a relay of two cooperating contact members, means for movover the same path and means associated with each of said contact members and so proportioned that for the same actuating current one of said contacts has a lesser natural distance of travel than the other.

9. The combination in a relay of! two cooperating contact members, means for moving each of said contacts over the same path in the same direction, and means associated with each of said contact members and so proportioned that for any actuating current above a predetermined amount one of said contact members has a greater natural distance of travel than the other of said contacts, the difference between the two distances increasing with increase of actuating current 10. The'combination in a relay of two normally separated contacts, a current actuated means for moving each of said contacts over the same path in the same direction, means for permitting one of said contacts. to move with greater rapidity than the other contact, and means for opposing the action of said actuating means. said actuating and opposing means being so related that for the same actuating current the faster moving contact has a lesser natural distance of travel than the slower moving contact.

11. The combination in a rela-v of two cooperating contacts, a current actuated means for moving each of said contacts over the same path in the same direction, means for causing one of said contacts to move with reater rapidity than the other, means associated with each of said contacts and so proportioned that for any actuating current below a predetermined amount the more rapidly moving contact has a greater natural distance of travel than the slower moving contact while for any actuating current above a predetermined amount the more rapridly moving element has a lesser natural distance of travel than the slower moving contact.

12. The combination in a relay of two normally separated contacts, actuating means for moving each of said contacts over the same path in the same direction, means for causing one ofsaid contacts to move ahead of the other contact, and means associated with each of said contacts and so proportioned that with the same value of actuating current above a predetermined amount the following contact will overtalce the leading contact after the latter has reached the end of its natural travel.

13. The combination in a relay of a rapidly moving current actuated element having a limited natural distance of travel for any actuating current above a predetermined amount, a slowly moving current actuated element having for the same actuated current a greater natural distance of travel, a contact moved by said rapidly moving element, a cooperating contact moved lry Said;

slowly moving elementto follow said first mentioned contact in the same path, and means cooperating with said elements and so proportionedthat said coiiperating contact overtakes said first mentioned contact when the actuating current exceeds a predetermined amount.

14. The combination in a relay of a rapidly moving meter element having a limited path as the first contact member said contact members being normally separated from each other and the meter elements being so proportioned and related to each other that the second contact will overtake the first when the actuating current exceeds a predetermined amount.

15. The combination in a relay of a rapidly moving contact element having a limited natural distance of travel for any actuating current above a. predetermined amount, a se cond more slowly moving contact element having a greater natural distance of travel for the same actuatin current, actuating means for moving each of said contact elements in the same path and in the same direction, said contact elements and so proportioned that the second contact will overtakethe first mentioned contact when the actuating current exceeds a predetermined amount and that thetime required for the second contact to overtake the first after the excess current has been applied will vary as an inverse function of the applied current.

16. The combination in a relay of a rapidly moving meter element having a limited scale deflection, a second more slowly moving meter element having a greater scale deflection than the first for any given current, a contact member attached to the first element and a second contact member attached to the second element so as to follow the same path as the first contact member said contact members being'normally separated from each other and the meter element being so proportioned and related to each other that the second contact will overtake the first when the actuating current exceeds a predetermined amount, and that the time required for the second contact to overtake the first after the fication requiring correction as element Patent Ofiice.

[seen] and means associated with each of an improvement in Time-Limit Relays,

Signed and sealed this 12th day'of February, A. D., 1913.

eXceSs current has been applied will vary as an inverse function of the applied current.

17. An overload relay comprising a first and a second contact movable over the same path in the same direction into engagement, means operatively related to each contact and so proportioned that upon the occurrence than the second contact in the same direction into engagement, means operativ-ely related to each contact andso proportioned that upon the occurrenceof an overload above a predetermined amount the second contact will always move over a greater path than the first contact, means operatively related to each contact and so proportioned that the first contact has a greater speed of movement than the second contact,

said first contact being so positioned that the second contact alway engages the game before it reaches thelimit of its natural path of movement whereby firm and positive engagement of the contact is made.

In witness whereof, I have hereunto set myhand this 1st day of September, 1914. JAMES R. CRAIGHEAD. Witnesses:

BENJAMIN B. HULL, HELEN ORroRn.

It is hereby certified that in Letters Patent N 0. 1,250,806, granted December 18, 1917, upon theapplication of James R. Craighead, of Schenectady, New York, for I an error appears in the printed specifollows: Page 5, line 36, claim 16, for the word read elements; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the casein the J. T. NEWTON,

Gammissioner of Patents. 

